The present invention relates to reducing electric field emissions from electrical appliances.
Electrical appliances such as Cathode Ray Tube (CRT) displays for television reception or computer visual display output comprise cathode ray tube drive circuits that generate magnetic, electric and electrostatic fields. These fields can radiate from the displays. Conventionally, electric field emissions from CRT displays are split into two bands known as Band I and Band II. Band I extends from 5 Hz to 2 KHz. Band II extends from 2 kHz to 400 kHz. Techniques have been developed to reduce magnetic and electrostatic field emissions from CRT displays but not to reduce electric field emissions.
In use, a conventional CRT display radiates an electric field in the Band I from its mains power cable connecting the display to the mains electricity supply. The electric field is radiated because the mains voltage signals on the Live and Neutral conductors are unbalanced. In a CRT display with conventional three wire ("Live" or "Line", "Earth" or "Ground", and "Neutral" or Return") mains power connection, the electric field emissions can be significantly reduced by shielding the mains power cable with electrically conductive sleeving connected to Earth. However, in a CRT display with conventional, two wire ("Live" or "Line" and "Neutral" or "Return"), double insulated, mains power connection, there is no earth to which electrically conductive sleeving may be connected.